Power window control systems in vehicles have individual switches to control an associated motor for opening or closing an associated window. The switches are typically located near the associated window. In addition such systems include a master power window switch assembly. Each window has an associated switch in the master power window switch assembly, hereinafter also referred to as a master switch assembly. The master switch assembly is typically located near the driver of the vehicle and provides individual and/or group control of all the windows in the vehicle.
In power window systems, overcurrent protection provided between individual motors and associated switches is known. Overcurrent protection for each individual motor may be adequate to protect an individual motor circuit from damaging overcurrents, however, individual motor circuit overcurrent protection does not necessarily provide adequate protection for a printed circuit board of the master switch assembly.
Foreseeable operating conditions for a master switch assembly printed circuit board include conducting electrical currents resulting from (i) multiple normal window opening/closing, and/or (ii) multiple electric motor stall conditions. A motor stall condition occurs when the window reaches a mechanical stop, or is prevented from movement, and the window switch is still actuated, thereby continuing to supply current to the motor. Motor stall conditions draw current levels in the motor circuit substantially greater than current levels during normal opening/closing. Further, it is foreseeable that more than one window motor may be in a motor stall condition at the same time. The multiple motor stall condition, and the substantially higher associated current levels, is a factor in circuit design and overcurrent protection design.
For example, a circuit board may conduct 32 amps if all switches are actuated in a normal open/close operation. The same circuit board may experience current levels of 100 amps if all switches are actuated and their associated motors are in a motor stall condition. The foreseeable 100 amp load is an important factor in circuit board design and electrical component design. Consequently, printed circuit board conductive traces and electrical components are designed to withstand the higher potential current levels that may result from foreseeable operating conditions instead of normal operating circuit requirements.